Electrical conductor



Dec. 22, 1942. o. A. FREDERICKSON 2,306,159

ELECTRICAL CONDUCTOR Filed March 11, 1940 PLAST/C/ZL'D RES/N I NSULA TING WAX ENVELOPE B/u/a cs/w/m/ W/RE PLAS TIC/ZED IEES/N INSULATING WAX [NI 1. OPE CPUMPL 0 PAPER 0WD! TH WIPE INVENTOR Patented Dec. 22, 1942 ELECTRICAL CONDUCTOR Otto A. Fredcrickson, Glen Ridge, N. J., asslgnor to National Electric Products Corporation, a

corporation of Delaware Application March 11, [1940, Serial No. 323,372

6 Claims.

This invention relates to an electrical conductor.

In accordance with the best modern practice and this is particularly true of the type of electrical conductors known as building" wire, the current-carrying element of the conductor, consisting of a single wire of electrically conductive material or a plurality of such wires, is surrounded by a dielectric sheath, such as a sheath of solid rubber, a wrapping of impregnated cambric, or other suitable dielectric enclosing medium. Around such dielectric sheath there is a covering of yielding, and typically fibrous, material, such as a braided, woven, or knit structure of cotton yarn, twisted paper, or other suitable material. The fibrous covering is impregnated with a saturant of moisture-resistant and flameretardant sort, such as a bituminous saturant. In order to give a hard finish and ready fishability to the conductor, there is a coating of paint over the saturated fabric covering, and this paint coating is waxed or otherwise enduringly lubricated.

Taking such conductor as exemplifying preferred prior practice, the object of my invention is in such general assembly to improve, and desirably to simplify, the conductor assembly by incorporating in the assembly a novel element cooperative with the several elements of the preexisting structure if all such elements be present, and providing for the elimination of certain such elements it simplification in the conductor structure be desired.

To the above end I associate in assembly with the yielding covering of the conductor a thin protective envelope, rubber-like in its elasticity, but non-rubber-like in other inherent qualities, which, by the yielding covering which it overlies, is so supported in the assembly that it is protected from mechanical injury, such as puncture and tearing, and, which, in the assembly, gives moisture-resistant, oil-resistant, and flameretardant protection to the yielding covering. In general equivalency to a fibrous covering of braided, woven, or knit fabric, the yielding covering for the conductor core may be a simple helical wrapping of yarn; or may be other material and structure adequately yielding to serve as a covering for the core and support for the envelope; such for example as a wrapping of crumpled paper, crumpled Cellophane, or the like. If the core covering be of non-absorbent material, such as crumpled Cellophane, it will not absorb a saturant, but in assembly with the protective envelope impregnation of the covering becomes of lesser moment.

In the accompanying drawing Fig. I is an elevational view progressively broken away, in which the novel assembly of my invention is exemplified by the assembly of the thin protective envelope with a core covering of braided yarn. Fig. II is a cross sectional view on an enlarged scale through the conductor shown in Fig. I, taken in the plane of the section line II-II of Fig. I. Fig. III is a' view primarily in elevation with the conductor elements progressively broken away, but partly in central longitudinal section, in which the novel assembly of my invention is exemplified by the association of the thin protective envelope with a yielding core covering in the form of a simple Wrapping of crumpled paper, crumpled Cellophane, or the like. Fig. IV is a cross sectional view on an enlarged scale through the conductor of Fig. III, taken in the plane of section line IV-IV of Fig. III.

Referring to the above described drawing in which embodiment of my invention is exemplified, the current-carrying core of the conductor is shown as comprising a dielectric sheath 2 of rubber as well as a copper wire forming the current-carrying element proper. Referring now particularly to the structure illustrated in Figs. I and II, the current-carrying core of the conductor is surrounded by an assembly consisting of a yielding and fibrous covering 3 of braided yarn surrounded by a thin structurally unitary elastic envelope 4. Over the envelope 4 there is indicated a coating 5 of wax to give a slick finish to the conductor.

The envelope 4 as above noted is a thin unitary and elastic sheath, and this sheath is also of oil-resistant and oxygen-resistant, moistureresistant and flame-retardant character. In its substance the envelope is rubber-like in its elasticity and toughness. It is more resistant to abrasion and puncture than is rubber, and is non-rubber-like in its characteristics of oil-resistance, oxygen-resistance, and flame-retardance. It presents lesser resistance to surface contact movement, or drag, than does vulcanized rubber. The conjunction of properties possessed by the envelope is provided adequately by plastic compositions. By the term plastic composition as I use that term, I mean a composition consisting of high polymers, or micelles.

of resinous sort plasticized to a rubber-like consistency and capable of being rendered fluid, 0r

workable, by the use of solvents, heat, or by utilizing both heat and solvents.

Compositions suitable for my purpose may be made of polyvinyl esters, such as polyvinyl chloride, the so-called copolymers of polyvinyl esters, acryloid resin, acryloid-paracoumarone blends, high polymer ketone resins, polystyrene resins, and other high-polymer resins having high tensile strength, and high resistance to aliphatic solvents; plasticized with suitable plasticizers, such'as di-butyl phthalate, di-amyl phthalate, tri-cresyl phosphate, acetyl ricinoleate, di-butyl tartrate, low melting glycerol phthalate, and other resin plasticizers. I may also use one of the available pre-plasticized resinous compositions, such as the aleuritinates and hydroxystearates of polyvinyl alcohols, or the butyreates of polyvinyl alcohols. Such compositions may be used with little or no additional plasticizer.

If desired, the plastic composition may be .applied by passing a prepared assembly of conductor core, and fabric covering therefor, through a bath consisting of plastic composition rendered fluid by suitable solvent, such as ethyl acetate, acetone, and the mono-ethyl-ether of ethyleneglycol, and by gentle heating. After passing through such bath, the coated assembly is wiped in dies.

My preferred procedure is to heat the plastic composition, with or without the addition of a small quantity of solvent, to a workable consistency. The plastic composition is then wiped on the prepared assembly, in the manner in which unvulcanized rubber is applied, to form a sheath surrounding the conductive element of the current-carrying core. Regarding this application, it should however, be understood that the plastic composition, having inherently greater toughness and cohesion than unvulcanized rubber, may be applied in a much thinner film.

The wiping effect desirably is produced in extrusion apparatus of the sort used in applying unvulcanized rubber around the current-carrying element of a conductor, but the substance of the envelope may otherwise be wiped on the core. In whatever manner the envelope material be applied, it is a matter of moment that it be applied in a thin film. If the film be very thin, plastic compositions which-would tend toward brittleness if applied in a thick coating, are adequately tough and elastic at all temperatures fully to satisfy my requirements. The thickness of film which I prefer to provide as the envelope for conductors of the smaller sizes is no more than about 2 or 340mm of an inch, and for the larger size conductors I prefer that the thickness should be no more than 8 or ii ths of an inch.

As exemplary of a plastic composition suitable for the film or envelope embracing the served covering, I may give a composition consisting of polyvinyl chloride plasticized to a rubber-like consistency with a plasticizer such as acetyl ricinoleate. Various suitable compositions consisting of high polymer resin and appropriate plasticizer may readily be made up in accordance with known practice in the art of making plastic compositions, having regard to the requisite properties of the protective envelope of my conductor structure. In them isobutylene polymers, having the character of a synthetic, unvulcanizable, rubber resistant to aliphatics and to oxygen, may suitably be included with the high polymer resin and plasticizer.

' It should be understood that the substance of the protective element is not, and should not be,

a saturant for the fibrous covering of the assembly; but on the contrary is, and should lie, as, a thin structurally unitary envelope around the fibrous covering. If, as is desirable, a saturant for the covering is used, it tends to adhere the envelope to the covering. In the conductor structure the yielding cover 3 and the elastic envelope 4 provide a cooperative assembly. In

such assembly the envelope by virtue of its characteristics which will be later more fully discussed protects the yielding covering, whlle the yielding covering for its part gives a backing for the thin elastic envelope which tends to protect the envelope against puncture, tearing, or cracking. It has been explained that as a very thin structurally unitary member, the envelope 4 is less susceptible to embrittlement, particularly at low temperatures, than is a thicker layer of analogous substance. It will be readily understood that the yielding backing provided by a covering, such as a covering of braided yarn, by permitting a slight yielding of the envelope in contact of the conductor with exterior objects, protects the envelope against mechanical injury by such contact.

It will be noted that in the assembly of Figs. I and II, the illustration of the conductor does not include coatings of pitch, or paint, overlying the envelope 4. Whereas such coatings may be applied, and whereas they provide additional protection to the interior of the conductor structure, they may generally be omitted from the assembly. This is because the envelope itself serves as a seal against the entrance of moisture; and because itis of itself oxygen-resistant, oilresistant, flame-retardant, and imparts the quality of ready fishability to the conductor. Also it is printable, so that identifying markings for the conductor may be printed upon it if a paint coating is omitted. Thus, merely as comprising the elements shown, the conductor may be used for various purposes, and may be even used as building wire.

Referring now particularly to Figs. III and IV of the drawing, the yielding covering 0 surrounding the current-carrying core of the conductor and supporting the elastic envelope 4 is, in those figures of the drawing, shown as an overlapped wrapping of crumpled paper or Cellophane applied in appropriate thickness, both protectively to surround the dielectric and yieldingly to support the envelope. If, of paper, or an analogous fibrous material, it may be impregnated with a suitable bituminous saturant. With a yielding covering of the sort shown in these figures of the drawing which is less integrated structurally than a braided, woven, or knit covering, the envelope 4 associated with it functions as an integrant, or binder element, holding the covering together and binding it to the conductive core of the conductor. In this respect the envelope 4 thus performs a secondary function analogous to that performed by a similar envelope in the conductor disclosed and claimed in my companion application Serial No. 323,371, filed March 11, 1940, in which the envelope functions as an integrant and binder for a single layer wrapping of yarn, or equivalent material, which forms a yielding covering for the current-carrying core of the conductor. Herein, however, the showing of Figs. III and IV is to be taken as exemplary of a wide range of other coverings which conform merely to the requirement that they be yielding, and that they have general suitability for use in the indicated position in the structure of. an electrical conductor of generally high quality. In Figs. III and IV, similarly to Figs. I and II, the envelope l of the conductor is shown as overlaid only by a coating of wax to give the conductor a slick finish and improved fishability. It may be understood, however, that insofar as the yielding covering for the current-carrying core supporting the envelope lacks inherent coherence, to such extent it becomes more desirable to overlie the envelope with one or more finishing coats of substances, such as pitch or paint, by their presence to supplement the integrating effect of the envelope in the conductor assembly.

I am aware that plastic composition as herein defined has been used in thick layers in, or as, the insulation of an electrical conductor. I am not aware that plastic composition has, prior to my invention, been used in assembly With a yielding covering for the current-carrying core of a conductor in a thin envelope protectively confining and yieldingly backed by such yielding corecovering.

Since the gist of my invention resides in the provision of a protective envelope characterized by the above noted qualities organized to envelope and be supported by a yielding covering surrounding a conductor core, I do not purpose to limit my invention to the use of any particular substances, or class of substances, for the said protective envelope, the above disclosure as to substances suitable for the envelope being exemplary. Also in the general conductor assembly, the rubber sheath shown as part of the conductor core may be replaced by a sheath of another suitable substance, or the current-carrying core may consist merely of the current-carrying element itself.

I claim as my invention:

1. In an electrical conductor including an inner conductive core, in combination a compressibly yielding fibrous protective jacket impregnated with bituminous saturant surrounding the conductor core, and a unitary, self-contained and non-saturant single elastic film composed essentially of a high-polymer synthetic resin plasticized to rubberlike consistency closely surrounding the said protective jacket, the said film diametrically confining the said jacket and being of a thickness not substantially exceeding .009 inch and being impervious to air and moisture.

2. In an electrical conductor including an inner conductive core, in combination a compressibly yielding protective jacket surrounding the conductor core, and a unitary, self-contained and non-saturant single elastic film composed essentially of a high-polymer synthetic resin plasticized to rubber-like consistency closely surrounding the said protective jacket, the said film diametrically confining the said jacket and being of a thickness not substantially exceeding .009 inch and being impervious to air and moisture.

3. In an electrical conductor including an inner conductive core, in combination with a compressibly yielding fabric protective jacket surrounding the conductor core, and a unitary, selfcontained and non-saturant single elastic film composed essentially of a high-polymer synthetic resin plasticized to rubber-like consistency closely surrounding the said protective jacket, the said film diametrically confining the said jacket and being of a thickness not substantially exceeding .009 inch and being impervious to air and moisture.

4. In an electrical conductor including an'inner conductive core, in combination a compressibly yielding fibrous protective jacket impregnated with bituminous saturant surrounding the conductor core, and a unitary, self-contained and non-saturant single elastic film composed essentially of high-polymer polyvinyl resin plasticized to rubber-like consistency closely surrounding the said protective jacket, the said film diametrically confining the said jacket and being of a thickness not substantially exceeding .009 inch and being impervious to air and moisture.

5. In an electrical conductor including an inner conductive core, in combination a compressibly yielding protective jacket, and a unitary, self-contained and non-saturant single elastic film composed essentially of high-polymer polyvinyl resin plasticized to rubber-like consistency closely surrounding the said protective jacket and being of a thickness not substantially exceeding .009 inch and being impervious to air and moisture.

6. In an electrical conductor including an inner conductive core, in combination with a compressibly yielding fabric protective jacket surrounding the conductor core, and a unitary, selfcontained and non-saturant single elastic film composed essentially of a high-polymer polyvinyl resin plasticized to rubber-like consistency closely surrounding the said protective jacket, the said film diametrically confining the said jacket and being of a thickness not substantially exceeding .009 inch and being impervious to air and moisture.

OTTO A. FREDERICKSON. 

